Cast part

ABSTRACT

The invention relates to a cast part.

The invention relates to a cast part, particularly as a chassisapplication.

For chassis applications, sub-eutectic Al alloys having a Si contentbetween 7 and 12 wt.-% are usually used. In gravity ingot mold casting,the alloy AlSi11Mg is frequently used; in low-pressure ingot moldcasting, the alloy AlSi7Mg is frequently used. Low-Si AlSiMg alloys,which are characterized by clearly improved mechanical properties ascompared with the common cast AlSi alloys mentioned above, are knownfrom WO 2007/025528 A2 and WO/2009/059593.

Proceeding from this state of the art, the invention is based on thetask of further improving a cast part made from a low-Si Al alloy withregard to its mechanical properties.

This is achieved, according to the invention, by means of a cast partmade from an Al casting alloy that contains at least five of the alloycomponents listed below

-   Si: 2.5 to 3.3, preferably 2.7 to 3.1 wt.-%,-   Mg: 0.2 to 0.7, preferably 0.3 to 0.6 wt.-%,-   Fe: <0.18, preferably 0.05 to 0.16 wt.-%,-   Mn: <0.5, preferably 0.05 to 0.4 wt.-%,-   Ti: <0.1, preferably 0.01 to 0.08 wt.-%,-   Sr: <0.03, preferably 0.01 to 0.03 wt.-%,-   Cr: 0.3 to 1.3, preferably 0.4 to 1.0,    -   particularly preferably 0.5 to 0.8 wt.-%,-   Others: <0.1 wt.-%,    and is supplemented to 100 wt.-% with Al, in each instance,

wherein the cast part is artificially aged between 150 to 240° C. for 15to 120 minutes, preferably for 15 to 60 minutes, particularly preferablyfor 20 to 55 minutes, very particularly preferably for 30 to 55 minutes,and absolutely particularly preferably between 30 and 45 minutes.

It can be advantageous if the cast part is artificially aged between 170to 230° C. for 15 to 120 minutes, preferably for 15 to 60 minutes,particularly preferably for 20 to 55 minutes, very particularlypreferably for 30 to 55 minutes, and absolutely particularly preferablybetween 30 and 45 minutes.

It can be practical if the cast part is artificially aged between 200 to220° C. for 15 to 120 minutes, preferably for 15 to 60 minutes,particularly preferably for 20 to 55 minutes, very particularlypreferably for 30 to 55 minutes, and absolutely particularly preferablybetween 30 and 45 minutes.

A further advantage can consist in that the cast part issolution-annealed before artificial aging, between 490 and 550° C. for 1to 10 hours, preferably for 5 to 9 hours, particularly preferably for 6to 8 hours.

It can be advantageous if the cast part is solution-annealed beforeartificial aging, between 530 and 550° C. for 1 to 10 hours, preferablyfor 5 to 9 hours, particularly preferably for 6 to 8 hours.

The aforementioned heat treatments lead to a further significantimprovement in the mechanical properties of the cast component or of thecast part.

For chassis applications, particularly for wheel-guiding components,increased mechanical characteristic values are obtained in this way, intotal.

The alloys according to the invention can contain production-relatedcontaminants, for example Pb, Ni, Zn, etc., as they are generally knownto a person skilled in the art. Such contaminants are included amongwhat are called the other alloy components.

The cast parts according to the invention particularly demonstrateimproved strength as compared with conventional cast parts or cast partsthat are not heat-treated at all, but also demonstrate an improvedstrength/elongation ratio.

Fundamentally, a permanent mold method is suitable as a productionmethod for heat-treated cast parts for or of chassis parts of motorvehicles, in particular, according to the invention. Because of the verygood mechanical properties of work pieces, components, or parts that aresubject to great stress, gravity ingot mold casting and low-pressureingot mold casting are particularly suitable as production methods.

In the case of pressure-supported casting methods, in particular, forexample the low-pressure counter-pressure casting method (CPC method),semi-solid casting method, as well as other pressure-supported castingmethods such as squeeze-casting, casting-forging (Cobapress), or moldsystem-automated low-pressure sand-casting, better mechanicaltechnological properties result from the good casting structure. In thisconnection, the counter-pressure ingot mold casting method (CPC method)is particularly preferred.

Aside from the advantages already mentioned, which cast partsheat-treated according to the invention demonstrate, in addition thecorrosion resistance of the cast parts is significantly increasedbecause of the absence of the alloy components Cu and Zn. Such castparts are also relatively inexpensive, because no alloy additives thatmake them more expensive, such as rare earth metals, for example, areused; the usual melt treatment can be applied, and no particular effortfor separating the circulation is required.

EXAMPLE

For a determination of the mechanical properties of a heat-treated castpart, pivot bearings made of the alloy AlSi3Mg0.5Cr0.7 are cast usingthe low-pressure counter-pressure ingot mold casting method, and tensilerods are produced from these, according to DIN 50125:2009-07.Subsequently, solution annealing takes place at 545° C. for 0.5 to 6hours, as does artificial aging at 200-220° C., also for 0.5 to 6 hours.The mechanical properties of tensile strength R_(m), yield strengthR_(p)0.2, and elongation to rupture A5 are determined. DIN EN ISO6842-1: 2009-12 is used for this. The values determined are showngraphically in FIG. 1.

It is shown that in the case of artificial aging between 200 and 220° C.for less than 60 minutes, particularly for 30 to 59 minutes, asignificant increase in the elongation to rupture can be found, which isalso accompanied by an increase in the tensile strength. In thisconnection, the yield strength demonstrates a level that remainsapproximately the same.

1. Cast part made from an Al casting alloy, containing at least five ofthe alloy components listed below: Si: 2.5 to 3.3, preferably 2.7 to 3.1wt.-%, Mg: 0.2 to 0.7, preferably 0.3 to 0.6 wt.-%, Fe: <0.18,preferably 0.05 to 0.16 wt.-%, Mn: <0.5, preferably 0.05 to 0.4 wt.-%,Ti: <0.1, preferably 0.01 to 0.08 wt.-%, Sr: <0.03, preferably 0.01 to0.03 wt.-%, Cr: 0.3 to 1.3, preferably 0.4 to 1.0, particularlypreferably 0.5 to 0.8 wt.-%, Others: <0.1 wt.-%, and is supplemented to100 wt.-% with Al, in each instance, wherein the cast part isartificially aged between 150 to 240° C. for 15 to 120 minutes,preferably for 15 to 60 minutes, particularly preferably for 20 to 55minutes, and very particularly preferably for 30 to 55 minutes.
 2. Castpart, particularly according to claim 1, wherein the cast part isartificially aged between 170 to 230° C. for 15 to 120 minutes,preferably for 15 to 60 minutes, particularly preferably for 20 to 55minutes, and very particularly preferably for 30 to 55 minutes.
 3. Castpart, particularly according to claim 1, wherein the cast part isartificially aged between 200 to 220° C. for 15 to 120 minutes,preferably for 15 to 60 minutes, particularly preferably for 20 to 55minutes, and very particularly preferably for 30 to 55 minutes.
 4. Castpart, particularly according to claim 1, wherein the cast part issolution-annealed between 490 and 550° C. for 1 to 10 hours, preferablyfor 5 to 9 hours, particularly preferably for 6 to 8 hours.
 5. Castpart, particularly according to claim 1, wherein the cast part issolution-annealed between 530 and 550° C. for 1 to 10 hours, preferablyfor 5 to 9 hours, particularly preferably for 6 to 8 hours.
 6. Use of acast part according to claim 1 as a component or part for or of chassisparts of motor vehicles.